bresenham_circle.dart

import 'dart:ui';

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

List<Offset> getBresenhamCirclePoints(
  Offset center,
  double radius,
) {
  List<Offset> points = [];
  int x = 0;
  int y = radius.toInt();
  int d = 3 - 2 * radius.toInt();

  points.add(center);

  while (x <= y) {
    // 0
    points.add(Offset(center.dx + x, center.dy - y));

    // 90
    points.add(Offset(center.dx + y, center.dy + x));

    // 180
    points.add(Offset(center.dx + x, center.dy + y));

    // 270
    points.add(Offset(center.dx - y, center.dy + x));

    // Another angel
    points.add(Offset(center.dx - x, center.dy - y));
    points.add(Offset(center.dx - x, center.dy + y));
    points.add(Offset(center.dx + y, center.dy - x));
    points.add(Offset(center.dx - y, center.dy - x));

    if (d > 0) {
      y -= 1;
      d = d - 4 * y;
    } else {
      x += 1;
      d = d + 4 * x + 6;
    }
  }

  return points;
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Bresenham Circle'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Container(
          decoration: const BoxDecoration(
            color: Colors.black,
          ),
          width: 200,
          height: 200,
          child: CustomPaint(
            size: const Size(200, 200),
            painter: BresenhamCircle(),
          ),
        ),
      ),
    );
  }
}

class BresenhamCircle extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    var paint = Paint()
      ..color = Colors.red
      ..strokeWidth = 5;

    Offset center = const Offset(100, 100);
    List<Offset> points = getBresenhamCirclePoints(center, 100);

    canvas.drawPoints(
      PointMode.points,
      points,
      paint,
    );
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return true;
  }
}